Primary irradiation of canine intracranial masses

Twenty-nine dogs received primary radiation therapy for intracranial lesion s and clinical signs suggestive of neoplasia. Presumptive diagnosis and tum or categorization was based on computed tomographic or magnetic resonance i mages. Meningioma was the most likely tumor type in 22 dogs and glioma or c horoid plexus tumors were tentatively identified in 4 and 3 dogs, respectiv ely. Cobalt-60 radiation was delivered in 3 Gy fractions on a daily, Monday -through-Friday basis for a total dose of 48 Gy (16 fractions) in 28 dogs; one dog received 54 Gy, Two of 29 dogs died during treatment of signs sugge stive of progressive tumor growth but were included in the overall evaluati on of response to treatment. Median overall survival was 250 days (range 21 -804), Mild acute radiation effects on normal tissue developed and did not influence outcome in any dog. Late radiation effects could not be evaluated in this study. No significant predictive indicators were identified from t he clinical or imaging data. Radiation therapy is superior to medical treat ment of brain tumors in dogs with steroids, is useful for tumors that are n ot currently operable and may be preferable to surgical resection in dogs i f the mass appears infiltrative. However, 22/29 (76%) dogs died of recurren t progressive neuropathy suggestive of tumor regrowth or progression. Thus, alternative methods for delivery of radiation to dogs with brain tumors or novel combinations of therapy should continue to undergo evaluation.